1. Field of the Invention
This invention relates to water treatment mechanisms and more particularly to water treatment devices including means for automatic disinfection of the devices at predetermined intervals.
2. Description of the Prior Art
Bacteriological contamination of water and other fluids has been officially recognized since the adoption of standards by the United States Public Health Service in 1911. However, only recently have other more potentially serious forms of contamination been suspected. In the last few years, tests have been conducted on inorganics such as heavy metals, and suspected carcinogenics, and on organics such as pesticides, herbicides and the like. With the development of more sophisticated and increasingly sensitive test equipment and procedures, the list of potentially dangerous substances is growing at a rapid rate. For example, the list of potentially dangerous long train molecular compounds is currently estimated at over 17,000.
Bacteriological control has long been accomplished by what has been referred to as a demand/residual principle of disinfection. For example, when bacteria in a domestic water supply is at an unacceptably high level, chlorine is added to the water and the residual chlorine provides a bactericidal action. Recently, the demand/residual principle of disinfection itself has become suspect of contributing to the water quality problem. Clinical experiments have linked chlorine with certain types of heart disease and allegations have been made that it combines with select inorganics to produce carcinogens.
There is a growing belief in the need for abandoning, or at least altering, the residual principle of disinfection.
As is well known, water treatment devices may be in several forms such as for example, filtering devices, dealkalizers, demineralizers, water softeners and the like, and the following although described in regard to water softeners in particular, will be understood to apply to any water treatment device of the type in which water is passed through a media bed for treatment purposes.
In the case of water softeners in particular, the media bed is usually in the form of an ion exchange resin, and raw water, normally supplied from a municipal water plant is passed through the bed and a chemical interaction occurs so that the hardness components in the water, such as calcium and magnesium ions are replaced by other ions such as sodium. After a period of time, the softening capability of the bed will become exhausted and the medium will have to be rejuvenated and such is normally accomplished by passing a brine solution through the bed, as will hereinafter be discussed.
Since by law, potable water can contain a number of harmless bacteria indigenous to municipally treated water, the potential for a build up or growth of such bacteria trapped in the tank and treatment bed of water softeners does exist. The relatively low level of bacteria in municipally treated water along with the organic compounds normally present in the water become trapped in the tank and in the water treatment bed. The organic compounds provide a nutrient for the bacteria thus turning the tank and the treatment bed into a breeding ground for bacterial growth.
Bacterial levels in water softeners, and in other water treating devices, are not a linearly escalating problem in that the bacteria level will decrease somewhat after each period of water flow and after each regeneration cycle. However, this alone will not control bacteriological contamination in that water softeners, particularly those located in private residences, are subject to long periods of nonflow, such as overnight and during vacation periods. For many years however, this flushing along with the residual disinfection provided by municipalities, was all that was accomplished in the line of bacteriological contamination control, in that the water softener and other treatment devices being a contributing factor to an already less than ideal water quality problem, was not recognized by the public, industry, or regulatory agencies.
The problem of water treatment systems acting as a bacteria breeding ground was recognized as a result of the water softening industry attempting to upgrade its equipment and service. Such upgrading occurred as a result of the unpleasant odors and tastes of the water in many parts of the country, such as those well known to accompany water that has been chlorinated by a municipality. To overcome this objectionable odor and taste problem, the water softening industry started incorporating a filter medium, such as activated carbon, in the water treatment bed, and such a water softener was renamed a water conditioner. However, the filter medium itself proved to be an excellent bacteria breeding ground, and the existing problem was compounded by such filter mediums and the fact that softeners and the other water treatment devices act as a breeding ground soon became recognized as a problem.
The next step in the development of the water softening art resulted upon recognition of the above described problem, and that step included the incorporation of a bactericidal disinfectant in the filter medium. The bactericidal disinfectant in most common usage today is a silver impregnated carbon which thus combines the filtering and the bactericidal functions into a single compound placed in the treatment bed of the water conditioner system itself. The filter/bactericidal medium is of such a nature that it requires periodic replacement and this leaves the water softening industry with two basic types of systems. The first of these basic types of systems is a fixedly installed self-regenerating system in which the ion exchange resin bed is automatically rejuvenated at predetermined intervals by hydraulically isolating the bed from the downstream portion of the water supply system and back flushing the bed with a brine solution and following the brine solution with a water rinse and then hydraulically coupling the rejuvenated bed back into the water supply system. Such a system does not normally include a filter/bactericidal medium due to the undesirable bacterial breeding capabilities of the filter medium and the need for replenishing the bactericidal medium due to its sacrificial type of usage. Thus, it will be seen that such in situ systems rely solely on the flushing of bacteria from the tank and the residual chlorine added by the municipality.
The second, and more common system currently being employed is one wherein the entire water treatment media tank and its contents are replaced periodically by a water servicing company. Such a system is fully disclosed in U.S. Pat. No. 3,078,224, and operates as follows: briefly, the tank containing the water treatment media bed and the filter/bactericidal medium is mounted in a building's water supply system by suitable quick disconnect fittings, and at predetermined intervals, depending on usage, a water service company will replace the spent tank with a regenerated tank. The spent tank is then transported to a central facility where a plurality of such tanks are emptied into a large vessel for batch regeneration and disinfection of the water treating media. The filter/bactericidal medium is removed and discarded during the batch regeneration cycle. The regeneration is accomplished by flushing with a brine solution and the disinfection is accomplished by a chlorine rinse and soft water is used as a final rinse. When these steps have been accomplished, the individual tanks are then refilled, a new supply of filter/bactericidal medium is added and the tanks are then ready for reuse.
This second type of prior art system, while being somewhat of an improvement over those systems which relied solely on flushing for control of bacterial contamination, are quite costly and inconvenient from a customer's standpoint, and are less than a completely satisfactory answer to the bacteriological contamination problem with regard to the water conditioning art. In the first place, the need for periodically opening a building's water distribution system for tank replacement purposes, subjects the system and the tanks themselves to the introduction of airborne bacteria and other contaminants. Secondly, the tank replacement interval is not something which occurs automatically at regular intervals, but is subject to varying work load requirements, delivery problems, scheduling delays, and the many factors which can cause the service company to interrupt or delay tank replacement. In the event that tank replacement is excessively delayed, the system can, at best, become totally ineffective and in some instances, can contribute significantly to the bacteriological contamination problem due to the fact that the filter medium and the water treating medium are excellent breeding grounds. Thirdly, since the system operates on the residual disinfection principle, that in and of itself is suspect as hereinbefore discussed, in that far too little is known relating to the combining of bactericidal disinfectants with the many and varied substances that may be contained in the water being treated.
Therefore, the need exists for a new and useful apparatus and method for automatic disinfection of water treatment equipment and the treatment bed thereof, which overcomes some of the problems and shortcomings of the prior art.